Cutting mechanisms are used in the harvesting of agriculturally cultivated plants in order to cut the plants, bring them together and feed them to a harvesting machine in which they are processed further, in particular threshed (combine harvester) or chopped (field chopper). Cutting mechanisms of this type generally comprise a front cutter bar in order to cut the plants, a reel which is arranged above the cutter bar, in order to gather the upper parts of the plants to the rear, and a transverse conveyor worm which brings the crop together laterally in order to feed same through a rear opening in a rear wall of the cutting mechanism to a feeder housing of the combine harvester or to feed the crop to a drawing-in channel of the field chopper to produce whole plant silage. Side walls between which the cutter bar and the transverse conveyor worm extend are provided at the lateral ends of the cutting mechanism. The base of the cutting mechanism between the cutter bar and the rear wall is formed by a bottom plate referred to as a cutting table.
For adaptation to different types of crop and therefore plant sizes, cutting mechanisms with length-adjustable cutting tables are used. In particular for harvesting rape, the cutting table is extended forward (and supplemented by side blades), whereas, by contrast, said cutting table is retracted to the rear when harvesting lower plants or plants which unlike rape form a tight bush, such as, for example, wheat.
In particular in the case of cutting mechanisms with length-adjustable cutting tables, but also in the case of cutting mechanisms which are not length-adjustable, the drive of the cutter bar has proven relatively complicated since the driving torque from the combine harvester has to be transmitted entirely to the front to the cutter bar. In the prior art, the drive of the cutter bar customarily takes place by means of a driving belt which is arranged at a lateral end of the cutting mechanism and transfers the driving torque provided by the combine harvester forward to a gearing which, by means of an eccentric drive, converts the rotational movement into a linear reciprocating movement of the cutter bar (cf. DE 10 2004 037 580 A1 for a rigid cutting mechanism or EP 1 653 122 A1 for a cutting mechanism with a length-adjustable table), or the driving belt is replaced by a telescopic propeller shaft (EP 2 700 294 A2).
In the case of cutting mechanism widths of relatively large working widths, it is expedient to divide the cutter bar into two parts which are driven in counter phase in order to eliminate the vibrations caused by the reciprocating movement of the cutter bar. The drive here of the cutter bar halves of each end of the cutting mechanism can take place here by means of an associated gearing, the outputs of which are phase-displaced in relation to each other by 180° (U.S. Pat. No. 3,577,716 A), or, starting from the center of the cutting mechanism, by means of a gearing with a crankshaft which drives two phase-offset outputs (U.S. Pat. No. 5,497,605 A). Other drives arranged in the center of the cutting mechanism use eccentric drives driven via planetary gearings for converting the rotational movement of a hydraulic motor into the lateral movement of the cutter bar halves (EP 2 382 852 A2), or a gearing which is arranged on the rear wall of the cutting mechanism and converts the incoming rotational movement into a linear movement of a drive rod, said linear movement being directed forward and rearward in an alternating manner and being converted into a lateral movement by single-part angle levers (cf. DE 10 2010 040 870 A1 which is considered as forming the generic type).
In particular (but not only) in the case of cutting mechanisms with length-adjustable cutting tables, in the center of the cutting mechanism only a relatively limited vertical space is available in which a gearing for converting the incoming rotational movement into a lateral movement of the cutter bar halves can be installed. However, the crankshaft of U.S. Pat. No. 5,497,605 A requires a relatively large vertical construction space, and this is also true for the combined planetary and eccentric drives arranged one above the other of EP 2 382 852 A2, while the arrangement according to DE 10 2010 040 870 A1 has the disadvantage that the coupling points at which the cutter bar halves are attached to the angle levers not only move to the side, but also to a certain extent forward and rearward since they pivot to and fro about the rotational axes of the angle levers. This movement forward and rearward requires an undesirable wear-promoting play in the bearings for the lateral guidance of the cutter bars. If the mentioned cutter bar movement taking place forward and rearward is intended to be limited, the angle levers have to have a very long design, which makes the drive relatively large and heavy.
An object of the invention is to provide a drive arrangement for driving a cutter bar with gearing for converting the incoming rotational movement into a lateral movement of the cutter bar which is thin in the vertical direction and also does not have the disadvantages mentioned with regard to DE 10 2010 040 870 A1, or has said disadvantages to a lesser extent.